Deploy in AWS

[KokTeng00]

Hello, can I ask is it possible to deploy the fastapi_mcp in the aws lambda and access the endpoint through my IDE with the defined mcp_config.json?

[KokTeng00]

This is the mcp_config.json that I have:

{
"mcpServers": {
"remote-example": {
"command": "npx",
"args": [
"mcp-remote",
"https://{api-id}.execute-api.{region}.amazonaws.com/{stage}/mcp",
"--header", "x-api-key:",
"--header", "Content-Type: application/json"
],
"disabled": false
}
}
}

But I am getting the error as

Error: failed to initialize server: <truncated 10 bytes> ing automatically selected callback port: 12644 [45916] Using custom headers: {"x-api-key":"","Content-Type":" application/json"} [45916] [45916] Connecting to remote server: https://{api-id}.execute-api.{region}.amazonaws.com/{stage}/mcp [45916] Using transport strategy: http-first [45916] Connection error: Error: Error POSTing to endpoint (HTTP 403): {"message":"Missing Authentication Token"} at StreamableHTTPClientTransport.send (file:///Users/ngkokteng/.nvm/versions/node/v18.20.8/lib/node_modules/mcp-remote/dist/chunk-OUCHRS4S.js:6558:15) at process.processTicksAndRejections (node:internal/process/task_queues:95:5) [45916] Fatal error: Error: Error POSTing to endpoint (HTTP 403): {"message":"Missing Authentication Token"} at StreamableHTTPClientTransport.send (file:///Users/ngkokteng/.nvm/versions/node/v18.20.8/lib/node_modules/mcp-remote/dist/chunk-OUCHRS4S.js:6558:15) at process.processTicksAndRejections (node:internal/process/task_queues:95:5): server terminated. Click here to change your configuration.

Do I define something wrong in my config? @shahar4499 would you mind sharing your opinion? It will be really helpful for me, thank you in advance.

[SameerSenapati17]

the "Missing Authentication Token" error from API Gateway means your AWS Lambda + API Gateway endpoint isn’t matching the path you’re hitting from your MCP config.

When you deploy FastAPI to Lambda via API Gateway, API Gateway expects:

• The path to exist in the deployed API Gateway stage

• The HTTP method to match (POST in this case)

• The authentication header to match (if using API Key)

If any of those are wrong, API Gateway returns 403 Missing Authentication Token.

From your config:

"https://{api-id}.execute-api.{region}.amazonaws.com/{stage}/mcp"

That means your Lambda handler must be behind a route /mcp in API Gateway. If your API Gateway doesn’t have /mcp configured (or it’s just /), this request will 403.